Support disabling automatic use of TLS

⚠️ This issue respects the following points: ⚠️

• This is a bug, not a question or a configuration/webserver/proxy issue.
• This issue is not already reported on Github OR Nextcloud Community Forum (I've searched it).
• Nextcloud Server is up to date. See Maintenance and Release Schedule for supported versions.
• I agree to follow Nextcloud's Code of Conduct.

Bug description

Hello,

I came upon an issue with our Exchange send connector, that allows anonymous relay from some of our internal IP addresses.

Our connector advertises TLS but has no TLS Certificate bound to it (which is not a good thing), but in the past Nextcloud did not care and sent emails with no TLS using this same connector.

Recently, it seems that TLS is enforced by Symfony Mailer if STARTTLS is advertised at EHLO. And thus emails are not sent anymore, because of the aforementioned settings (or lack thereof) in our Exchange.

It worked perfectly in the past, so I don't know when emails started to be blocked, since no one told us and we stumbled upon it by chance.

After many attempts to troubleshoot the issue, it appears that Symfony added a new parameter in their 7.1 version, called "auto_tls" that allows it to not attempt TLS handshakes automatically:
https://symfony.com/doc/current/mailer.html#disabling-automatic-tls

Would it be possible to update Symfony and add this parameter reflecting it in config.php so that we could bypass TLS entirely, and avoid this kind of issues?

Kind regards.

Steps to reproduce

1. Try to send a test email using the administrator page
2. Email is not sent

Expected behavior

Email was working fine in the past, we should be able to bypass TLS entirely if we needed to.

Nextcloud Server version

29

Operating system

Debian/Ubuntu

PHP engine version

PHP 8.2

Web server

Apache (supported)

Database engine version

MariaDB

Is this bug present after an update or on a fresh install?

None

Are you using the Nextcloud Server Encryption module?

None

What user-backends are you using?

• Default user-backend (database)
• LDAP/ Active Directory
• SSO - SAML
• Other

Configuration report

{
    "system": {
        "instanceid": "***REMOVED SENSITIVE VALUE***",
        "passwordsalt": "***REMOVED SENSITIVE VALUE***",
        "secret": "***REMOVED SENSITIVE VALUE***",
        "trusted_domains": [
            "***REMOVED SENSITIVE VALUE***"
        ],
        "datadirectory": "***REMOVED SENSITIVE VALUE***",
        "overwrite.cli.url": "***REMOVED SENSITIVE VALUE***",
        "dbtype": "mysql",
        "version": "29.0.11.1",
        "dbname": "***REMOVED SENSITIVE VALUE***",
        "dbhost": "***REMOVED SENSITIVE VALUE***",
        "dbport": "",
        "dbtableprefix": "oc_",
        "dbuser": "***REMOVED SENSITIVE VALUE***",
        "dbpassword": "***REMOVED SENSITIVE VALUE***",
        "installed": true,
        "htaccess.RewriteBase": "\/",
        "ldapIgnoreNamingRules": false,
        "ldapProviderFactory": "\\OCA\\User_LDAP\\LDAPProviderFactory",
        "memcache.local": "\\OC\\Memcache\\APCu",
        "memcache.locking": "\\OC\\Memcache\\Redis",
        "redis": {
            "host": "***REMOVED SENSITIVE VALUE***",
            "port": 6379
        },
        "maintenance": false,
        "theme": "",
        "logfile": "\/var\/log\/nextcloud\/nextcloud.log",
        "loglevel": 2,
        "mail_smtpdebug": false,
        "skeletondirectory": "***REMOVED SENSITIVE VALUE***",
        "defaultapp": "files",
        "default_phone_region": "FR",
        "mail_smtpmode": "smtp",
        "mail_from_address": "***REMOVED SENSITIVE VALUE***",
        "mail_domain": "***REMOVED SENSITIVE VALUE***",
        "mail_smtphost": "***REMOVED SENSITIVE VALUE***",
        "mail_smtpport": "25",
        "mail_smtpstreamoptions": {
            "ssl": {
                "allow_self_signed": true,
                "verify_peer": false,
                "verify_peer_name": false
            }
        },
        "apps_paths": [
            {
                "path": "\/var\/www\/nextcloud\/apps",
                "url": "\/apps",
                "writable": false
            },
            {
                "path": "\/var\/www\/nextcloud\/apps_extra",
                "url": "\/apps_extra",
                "writable": true
            }
        ],
        "updater.release.channel": "stable",
        "mysql.utf8mb4": true,
        "mail_sendmailmode": "smtp",
        "mail_smtpauthtype": "PLAIN",
        "maintenance_window_start": 1
    }
}

List of activated Apps

Enabled:
  - activity: 2.21.1
  - bruteforcesettings: 2.9.0
  - calendar: 4.7.16
  - circles: 29.0.0-dev
  - cloud_federation_api: 1.12.0
  - comments: 1.19.0
  - contactsinteraction: 1.10.0
  - dashboard: 7.9.0
  - dav: 1.30.1
  - federatedfilesharing: 1.19.0
  - federation: 1.19.0
  - files: 2.1.1
  - files_downloadlimit: 2.0.0
  - files_pdfviewer: 2.10.0
  - files_reminders: 1.2.0
  - files_sharing: 1.21.0
  - files_trashbin: 1.19.0
  - files_versions: 1.22.0
  - impersonate: 1.16.0
  - logreader: 2.14.0
  - lookup_server_connector: 1.17.0
  - nextcloud_announcements: 1.18.0
  - notifications: 2.17.0
  - oauth2: 1.17.1
  - password_policy: 1.19.0
  - photos: 2.5.0
  - polls: 7.2.9
  - privacy: 1.13.0
  - provisioning_api: 1.19.0
  - recommendations: 2.1.0
  - related_resources: 1.4.0
  - serverinfo: 1.19.0
  - settings: 1.12.0
  - sharebymail: 1.19.0
  - support: 1.12.0
  - survey_client: 1.17.0
  - systemtags: 1.19.0
  - text: 3.10.1
  - theming: 2.4.0
  - twofactor_backupcodes: 1.18.0
  - updatenotification: 1.19.1
  - user_ldap: 1.20.0
  - user_status: 1.9.0
  - viewer: 2.3.0
  - weather_status: 1.9.0
  - workflowengine: 2.11.0
Disabled:
  - admin_audit: 1.19.0
  - contacts: 5.5.3 (installed 5.5.3)
  - encryption: 2.17.0
  - files_external: 1.21.0
  - files_rightclick: 0.15.1 (installed 1.6.0)
  - firstrunwizard: 2.18.0 (installed 2.1)
  - richdocuments: 8.3.7 (installed 8.3.7)
  - sharerenamer: 3.2.0 (installed 3.2.0)
  - suspicious_login: 7.0.0
  - twofactor_totp: 11.0.0-dev
  - user_saml: 6.1.3 (installed 6.1.3)

Nextcloud Signing status

No errors have been found.

Nextcloud Logs

{"reqId":"wGQkWm0Y1mIGQAJH99lB","level":0,"time":"2025-02-03T10:51:56+00:00","remoteAddr":"XXXXXXXXXXX","user":"XXXXXXXXXXX","app":"core","method":"POST","url":"/settings/admin/mailtest","message":"Sending mail to \"Array\n(\n    [XXXXXXXXXXX] => XXXXXXXXXXX\n)\n\" with subject \"Test des paramètres de messagerie\" failed","userAgent":"Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:128.0) Gecko/20100101 Firefox/128.0","version":"29.0.11.1","exception":{"Exception":"Symfony\\Component\\Mailer\\Exception\\TransportException","Message":"Unable to connect with STARTTLS.","Code":0,"Trace":[{"file":"/var/www/nextcloud/3rdparty/symfony/mailer/Transport/Smtp/SmtpTransport.php","line":253,"function":"doHeloCommand","class":"Symfony\\Component\\Mailer\\Transport\\Smtp\\EsmtpTransport","type":"->"},{"file":"/var/www/nextcloud/3rdparty/symfony/mailer/Transport/Smtp/SmtpTransport.php","line":194,"function":"start","class":"Symfony\\Component\\Mailer\\Transport\\Smtp\\SmtpTransport","type":"->"},{"file":"/var/www/nextcloud/3rdparty/symfony/mailer/Transport/AbstractTransport.php","line":72,"function":"doSend","class":"Symfony\\Component\\Mailer\\Transport\\Smtp\\SmtpTransport","type":"->"},{"file":"/var/www/nextcloud/3rdparty/symfony/mailer/Transport/Smtp/SmtpTransport.php","line":136,"function":"send","class":"Symfony\\Component\\Mailer\\Transport\\AbstractTransport","type":"->"},{"file":"/var/www/nextcloud/3rdparty/symfony/mailer/Mailer.php","line":45,"function":"send","class":"Symfony\\Component\\Mailer\\Transport\\Smtp\\SmtpTransport","type":"->"},{"file":"/var/www/nextcloud/lib/private/Mail/Mailer.php","line":232,"function":"send","class":"Symfony\\Component\\Mailer\\Mailer","type":"->"},{"file":"/var/www/nextcloud/apps/settings/lib/Controller/MailSettingsController.php","line":168,"function":"send","class":"OC\\Mail\\Mailer","type":"->"},{"file":"/var/www/nextcloud/lib/private/AppFramework/Http/Dispatcher.php","line":232,"function":"sendTestMail","class":"OCA\\Settings\\Controller\\MailSettingsController","type":"->"},{"file":"/var/www/nextcloud/lib/private/AppFramework/Http/Dispatcher.php","line":138,"function":"executeController","class":"OC\\AppFramework\\Http\\Dispatcher","type":"->"},{"file":"/var/www/nextcloud/lib/private/AppFramework/App.php","line":184,"function":"dispatch","class":"OC\\AppFramework\\Http\\Dispatcher","type":"->"},{"file":"/var/www/nextcloud/lib/private/Route/Router.php","line":331,"function":"main","class":"OC\\AppFramework\\App","type":"::"},{"file":"/var/www/nextcloud/lib/base.php","line":1060,"function":"match","class":"OC\\Route\\Router","type":"->"},{"file":"/var/www/nextcloud/index.php","line":49,"function":"handleRequest","class":"OC","type":"::"}],"File":"/var/www/nextcloud/3rdparty/symfony/mailer/Transport/Smtp/EsmtpTransport.php","Line":116,"message":"Sending mail to \"Array\n(\n    [XXXXXXXXXXX] => XXXXXXXXXXX\n)\n\" with subject \"Test des paramètres de messagerie\" failed","exception":[],"CustomMessage":"Sending mail to \"Array\n(\n    [XXXXXXXXXXX] => XXXXXXXXXXX\n)\n\" with subject \"Test des paramètres de messagerie\" failed"},"id":"67a09fdc3748a"}

Additional info

No response

Start with lib/private/Mail/Mailer.php and the Symfony Mailer SMTP transport shown in the failure trace, then inspect how mail settings are read from config.php. Determine where the automatic TLS option can be passed through and verify that the administrator mail test can send without a TLS handshake when configured.